Cellular adhesion mechanisms have been recognized as crucial elements regulating the targeting of individual cells to their sites of function. As such, investigation of cell adhesion properties is central to the study of skin pathophysiology. Adhesion determinants direct such critical features as the migration of normal and abnormal skin components in growth and wound healing, the metastatic properties of tumor cells and as the accumulation of leukocytes in the response to infection and the development of inflammatory disease. This Leukocyte Migration Core has been formulated based on a stated need of current SDRC investigators and is designed to draw on the considerable experience of its co-directors and consultants to provide advice and expertise in the design and execution of studies related to cell adhesion and leukocyte homing. The Specific Aims of the Leukocyte Migration Core are as follows: 1. To provide expertise in the planning, execution and analysis of cell adhesion protocols using established standard substrates as well as exploring novel or unknown substrates. 2. To provide instruction and equipment for the execution and analysis of studies employing the parallel plate flow chamber. 3. To provide instruction, equipment and assistance in the execution and analysis of intra vital based adhesion studies in ear skin, bone marrow and peripheral lymph node. For comparative analysis, model systems in cremasteric muscle, mesenteric vessels, Pyer's patches and lamina propria are also available. 4. To provide instruction and assistance in the planning, execution and analysis of skin -specific leukocyte homing in vivo employing defined models of cutaneous inflammation. Services to be provided by the Leukocyte Migration Core are divisible into support for in vitro binding studies, in vivo homing model systems and intravital microscopy techniques. Although considerable overlap and collaboration is predicted, Dr. Fuhlbrigge will provide primary support for in vitro core services at the Harvard Institutes of Medicine and Dr. von Andrian will provide primary support for intravital microscopy core services at the Center for Blood Research, with support for in vivo homing studies divided between facilities.